As discussed in the Kirk-Othmer Encyclopedia of Chemical Technology, cellulose is a natural polymer of anhydro-D-glucose units having an empirical formula of C.sub.6 H.sub.10 O.sub.5. Native cellulose can be dissolved and regenerated by a number of techniques to manufacture products such as rayon. Cellulose can be derivatized via the OH groups of its glucose units to form, for example, esters such as cellulose acetate, ethers such as methylcellulose and carbamates such as cellulose phenylcarbamate. Cellulose is composed of crystalline and amorphous regions. X-ray diffraction spectroscopy of the crystalline regions of cellulose reveals that cellulose has a different crystalline structure after it has been dissolved and then regenerated. The crystalline structure of native cellulose is classified as cellulose I. The crystalline structure of the different regenerated celluloses is classified as cellulose II, III or IV.
It is well known that enantiomers can be separated by liquid chromatography using an optically active stationary phase. Cellulose is a polymer of anhydro-D-glucose units. Native cellulose, derivatized native cellulose, regenerated cellulose and derivatized regenerated cellulose have all been used as the stationary phase in liquid chromatography to separate enantiomers.
The ability of any specific cellulose based liquid chromatographic stationary phase to separate any specific group of enantiomers depends primarily on the structure and chemistry of the enantiomers as they interact with the structure and chemistry of the cellulose. Thus, a specific cellulose based liquid chromatographic stationary phase will separate some enantiomers better than another cellulose based liquid chromatographic stationary phase. It is difficult to form some derivatives of cellulose without dissolving them. For example, it is difficult to form an aromatic acid ester or an aromatic carbamate of cellulose without dissolving it.
If the cellulose derivative is dissolved, then it must be precipitated before it can be used as a stationary phase for the liquid chromatographic separation of enantiomers. It is difficult to control the particle size and morphology of precipitated derivatized cellulose. The dissolved derivatized cellulose can alternatively be precipitated on a support, such as porous silica beads, but this is a difficult process and the resulting product is relatively expensive. Since liquid chromatography grade cellulose particles and fibers are commercially available which are relatively inexpensive, it would be an advance in the art of preparing derivatized cellulose for the separation of enantiomers if the cellulose could be derivatized without dissolving it.